PURPOSE: To restrain the decline in detection beam intensity for enhancing the position detecting precision by a method wherein, as for the irradiating beams of the first lattice pattern, the zero dimensional beams emitted in case of irradiating the second lattice pattern are used.
CONSTITUTION: The beams 8 emitted from a laser oscillator 7 are reflected by a mirror 6 to irradiate the second lattice pattern 5 on the second substrate 4 for emitting the ± primary reflected diffracting beams 9, 9' to a detection optical system through the intermediary of the mirror 6. The zero dimensional diffracting beams 11 and the ± primary beams 12, 12' out of the transmission diffracting beams are emitted to the first substrate 1 through a contraction projecting lens 3. The lens 3 is subjected to the aberration from the pattern detecting optical wavelength on the wafer side so that the zero dimensional diffracting beams 11 only may irradiate the first lattice pattern 2 not to make the resultant ± primary reflected diffracting beams 10, 10' focus on the substrate 4 due to the aberration from the pattern detecting optical system. Through these procedures, the detection beam intensity can be augmented to enhance the detecting precision.
KUROSAKI TOSHISHIGE
TERASAWA TSUNEO
KATAOKA KEIJI